The Voyager program, Exploration of the outer planets and interstellar space

On August 20, 1977, 45 years ago in 2022, NASA launched Voyager 2 and shortly after, on September 5, 1977, Voyager 1. The Voyager program is a scientific mission to gain knowledge of the outer planets of our solar system . Even though both probes have now left our solar system, they are still sending information back to Earth.

“great tour”

In 1965, the American aerospace engineer Gary Flandro discovered that once every 175 years Jupiter, Saturn, Uranus and Neptune, the 4 major outer planets, are arranged in such a way that it is possible to visit them in 1 mission. This is what astronomers call the “grand tour”. To visit all 4 planets on a mission, the spacecraft launch must take place between 1976 and 1980.

The 2 spacecraft, Voyager 1 and 2, were originally designed under the Mariner program. This program was designed by NASA to fly over the planets Mercury, Mars and Venus. A spaceship flies near a planet to make recordings. They are called Mariner 11 and 12. Later they get a separate status and hence a new name, 1st Mariner Jupiter-Saturn and later Voyager.

Gravity Pendulum or Gravity Push

The two probes weigh around 800 kilograms and are equipped with dozens of measuring instruments and cameras. They use the so-called gravitational pendulum or gravitational thrust: spacecraft fly over planets and thus gain speed. When fast enough to fly to the next planet, the probes are catapulted to the next target. Therefore, many kilometers can be covered in a relatively short time with relatively little fuel.

Voyager 2 was launched before Voyager 1, because Voyager 2 orbits in a different orbit than Voyager 1. Voyager 2 has a longer journey to the 2 outer planets. This causes the probe to launch first due to the position of the planets. Due to Voyager 1’s shorter orbit, it will pass its twin before arriving at Jupiter.

Read also : Apollo 11: Man on the Moon

Launch

Voyager 2 was launched on August 20, 1977. On September 5, 1977, it was Voyager 1’s turn. Voyager 1’s primary mission was to fly over Jupiter and Saturn and study the rings, the magnetic field and the weather. The second part of the mission consists of studying the limits of the influence of the sun and measuring the particles in the solar wind. The probe then explores interstellar space. Voyager 1 travels through space at a speed of 17 kilometers per second, covering approximately 523 million kilometers per year.

Voyager 1 began photographing Jupiter in January 1979. In March, the probe came closest to the planet. Voyager 1 captures spectacular images of the famous Great Red Spot on Jupiter. It is a persistent storm that is larger than 3 times the Earth. The probe photographs volcanic activity on Io, a moon of Jupiter. This is the first time that volcanic activity has been observed elsewhere in our galaxy.

“Particle of dust caught in a beam of light”

Voyager 1’s next stop is Saturn, with its moons and rings. The spacecraft came closest to the gas giant on November 12, 1980, when it was 64,200 kilometers from cloud cover. It sends the first high-resolution images of Saturn’s rings back to Earth. As a result, the planet’s gaseous atmosphere is found to consist almost entirely of hydrogen and helium. Voyager 1 also takes close-up photos of Saturn’s many moons.

After completing its main mission, Voyager 1 continues its journey through space. In 1990, the spacecraft turns its camera to Earth to take a picture of it. In the photo, Earth appears as a tiny blue speck against the endless darkness of space and is barely visible. The famous American astronomer Carl Sagan writes about this photo in his book Pale Blue Dot: A Vision of the Human Future in Space: “It is here. It is the house. It’s us. With everyone you love, everyone you know, everyone you have heard of, every human being that has ever existed, lived their life…every saint and sinner in the history of our species has lived here , on a speck of dust trapped in a beam of light.

Voyager 1 entered the space between the stars in August 2012, the so-called interstellar space and thus left our solar system. The probe is thus out of the influence of the solar magnetic field and the solar wind of the charged particles. This extreme limit of our solar system is called the heliopause. This makes Voyager 1 the first man-made object to leave our solar system.

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‘hibernation’

Voyager 2 takes longer to fly to the gas giants Jupiter and Saturn, then to the ice giants Uranus and Neptune. After the spacecraft has visited the 4 planets, it explores, like Voyager 1, the limits of our solar system and interstellar space.

The probe arrives on Jupiter a few months after Voyager 1 and studies the planet. Upon arriving at Saturn, Voyager 2 discovers a new moon near the planet, called Pan.

After 5 years of “hibernation”, Voyager 2 arrived on Uranus in 1986. It took pictures of the blue planet, composed mainly of hydrogen and helium. The temperature on Uranus is -216 degrees and a day lasts 5:25 p.m. Voyager 2 studies the auroras, auroras that produce high levels of radiation, leaving the moons of Uranus without an atmosphere. The probe takes close-up images of the moon Miranda. Additionally, Voyager 2 discovers 10 new moons near Uranus and 2 very small moons called Ophelia and Cordelia.

Neptune

In 1989 Voyager 2 arrived at its final planetary destination, Neptune. Neptune is the 8th planet in the solar system and the farthest from the sun. The sky-blue planet, like Uranus, consists largely of hydrogen and helium, but also an abundance of water, ammonia and methane. The spacecraft observes storms of up to 2,400 kilometers per hour. Voyager 2 determines that a day on Neptune is 16.1 hours.

The probe also discovers 6 new moons and narrow rings. To avoid a collision with ice debris, Voyager 2 changes its orbit and flies over Triton, Neptune’s largest moon. There, we discover that there are geysers erupting on Triton. It is surprising that active volcanism occurs about 4.5 billion kilometers from the sun. After Voyager 2 leaves Neptune, the entire Voyager project is renamed Voyager Interstellar Mission.

Neptune, with Triton in the foreground.

On November 5, 2018, NASA announced that Voyager 2 had also left the solar system.

Voyager 1 is in interstellar space in this image, Voyager 2 is not there yet.

Future

In July 2022, Voyager 1 will be about 23.5 billion kilometers from Earth and Voyager 2 about 19.5 billion kilometers. NASA expects both Voyagers to run out of fuel in the coming years, resulting in loss of contact with the probes.

Voyager 1 and 2 are the only man-made objects that travel through interstellar space. In about 38,000 years, Voyager 1 will fly past the star Gliese 445 in the constellation Giraffe, less than 1.7 light-years away. Voyager 2 will approach “close” to a star after 40,000 years passing 1.7 light years from the small red dwarf Ross 248. Eventually, like stars in our galaxy, Voyagers will conform to the attraction gravity of the Milky Way and encircle its center forever.

gold record

Aboard Voyagers 1 and 2 is a gold disc composed by Carl Sagan. The plates contain sounds and images of the diversity of life and culture on Earth. The messages are intended for extraterrestrial life forms. However, the chances are very low that they intercept the probes and listen to the recordings. The plaques are therefore seen as a kind of calling card, not a serious attempt to communicate with possible extraterrestrial life forms.

The plate contains 116 images and various natural sounds, such as wind, lightning and animal sounds. Added to this are musical selections from different cultures and eras and spoken greetings from Earthlings in 55 languages. It also contains messages from former United States President Jimmy Carter and former United Nations Secretary General Kurt Waldheim. There is also a Dutch text recorded by Joan de Boer. If aliens listen to the record, she sends “warm greetings to everyone.”

(Source: NASA.gov, Nationalgeographic.nl, Sciencefocus.com, Metro.co.uk, Orbitaltoday.com, Wikipedia. Photos: ANP, Shutterstock)